WO2017209152A1

WO2017209152A1 - Wavelength conversion element, light source device, and image projection device

Info

Publication number: WO2017209152A1
Application number: PCT/JP2017/020163
Authority: WO
Inventors: 山口　裕; 阿部　雅之; 大古場　稔; 小川　大輔
Original assignee: キヤノン株式会社
Priority date: 2016-06-01
Filing date: 2017-05-30
Publication date: 2017-12-07
Also published as: US20210080815A1; JP6957463B2; US20190101814A1; US11347139B2; CN109313294B; JPWO2017209152A1; US10884329B2; GB201821316D0; DE112017002755T5; GB2568171A; GB2568171B; JP2022025065A; CN109313294A; PH12018502321A1

Abstract

[Problem] To inhibit the occurrence of a temperature gradient in a phosphor part due to irradiation with excitation light. [Solution] A wavelength conversion element 20 has a phosphor part 10 in which phosphor particles 5 are dispersed in a binder 4. The phosphor part has a first surface and a second surface located on opposite sides from each other in the thickness direction. The phosphor part is irradiated with excitation light from the second surface side. When the phosphor part is bisected in the thickness direction into a first portion on the first surface side and a second portion on the second surface side, the volume density of phosphor particles in the first portion is higher than the volume density in the second portion.

Description

Wavelength conversion element, light source device and image projection device

The present invention relates to a wavelength conversion element that emits excitation light with wavelength conversion to emit fluorescence light and a light source device using the same, and more particularly to a light source device suitable for an image projection device.

In the light source device as described above, fluorescent light is efficiently emitted by condensing excitation light such as laser light at a high density and irradiating the light to the phosphor layer of the wavelength conversion element. The phosphor layer is composed of a binder and phosphor particles dispersed in the binder.

However, when the excitation light is condensed and irradiated at a high density, the phosphor layer tends to have a high temperature, and there is a concern that the phosphor layer may be deteriorated or the luminous efficiency of the phosphor in the phosphor layer may be reduced.

Patent Document 1 discloses a method in which a phosphor layer in which phosphor particles are dispersed is formed in a binder made of an inorganic material, and the phosphor particles are brought into contact with a metal substrate to promote heat dissipation.

In the method disclosed in Patent Document 1, although the heat radiation promoting effect of the phosphor in the vicinity of the substrate in the phosphor layer can be expected, the heat radiation promoting effect of the phosphor particles in the vicinity of the incident surface irradiated with the excitation light is unknown. It is. Further, since the intensity of the excitation light to be irradiated is higher on the incident surface side, a locally large temperature difference (temperature gradient) occurs between the incident surface side portion and the substrate side portion in the phosphor layer, and this result There is a possibility that a crack etc. may occur due to the generated stress.

JP, 2015-94777, A

The problem is that the generation of the temperature gradient of the phosphor layer (phosphor portion) due to the irradiation of the excitation light can not be suppressed.

The wavelength conversion element as one aspect of the present invention has a phosphor portion in which phosphor particles are dispersed in a binder, and the phosphor portion has a first surface and a second surface opposite to each other in the thickness direction , And is a wavelength conversion element irradiated with excitation light from the second surface side. The wavelength conversion element has a first portion at the time when the phosphor portion is bisected in the thickness direction into a first portion on the first surface side and a second portion on the second surface side. The volume density of the phosphor particles is characterized by being higher than the volume density in the second part.

A light source device having a light source for emitting excitation light and the above wavelength conversion element also constitutes another aspect of the present invention.

In addition, an image projection apparatus including the light source device and an optical system that projects an image by modulating light from the light source device with a light modulation element also constitutes another aspect of the present invention.

Furthermore, the manufacturing method according to another aspect of the present invention includes a phosphor portion in which phosphor particles are dispersed in a binder, and the phosphor portion has a first surface and a second surface opposite to each other in the thickness direction. It is a manufacturing method of the wavelength conversion element which has a field and where excitation light is irradiated from the 2nd field side. In the manufacturing method, a first material in which phosphor particles are dispersed at a first volume density in a binder, and phosphor particles at a second volume density higher than the first volume density in a binder are dispersed. A second material is prepared, and the first material and the second material are laminated such that the second material is located on the first surface side.

According to the present invention, by controlling the density of the phosphor particles in the phosphor portion, it is possible to suppress the generation of the temperature gradient due to the irradiation of the excitation light and prevent the generation of the stress caused by the temperature gradient. It can be realized. Then, by using such a wavelength conversion element, it is possible to realize a light source device capable of stably generating fluorescent light and an image projection device capable of stably displaying a good projected image.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows the structure of the light source device which is Example 1 of this invention. The figure which shows the structure of the light source device which is a comparative example. FIG. 6 is a view showing excitation light traveling in the phosphor layer and temperature distribution in the phosphor layer in the light source device of Example 1. The figure which shows the temperature distribution in the excitation light which travels the inside of a fluorescent substance layer in a comparative example, and a fluorescent substance layer. The figure which compared the temperature distribution in the fluorescent substance layer of Example 1 and a comparative example. FIG. 6 is a view showing a modified example of the first embodiment. The figure which shows the structure of the image projection apparatus which is Example 2 of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of a light source device 100 according to a first embodiment of the present invention. The light source device 100 includes a light emitting element (laser diode) 1 as a light source, a wavelength conversion element 20, and a light source optical system 2. The light emitting element 1 emits a blue laser (about 450 nm wavelength) as the excitation light 6. The wavelength conversion element 20 has a substrate 3 and a phosphor layer (phosphor portion) 10 formed on the substrate 3 and supported by the substrate 3. The light source optical system 2 guides the excitation light 6 emitted from the light emitting element 1 to the wavelength conversion element 20 (phosphor layer 10).

The phosphor layer 10 is composed of a binder 4 and a plurality of phosphor particles 5 dispersed in the binder 4. The phosphor particles 5 absorb the excitation light 6 for wavelength conversion, and emit light of a longer wavelength (500 nm to 650 nm) than the excitation light 6 as fluorescent light 7. Moreover, the phosphor layer 10 diffuses (reflects or transmits) a part of the excitation light without wavelength conversion. The light source device 100 emits combined light (white light) of the fluorescent light 7 emitted from the phosphor layer 10 and a diffusion component (not shown) which is unconverted light in the excitation light.

The excitation light 6 emitted from the light emitting element 1 is condensed at high density by the light source optical system 2 and opposite to the substrate contact surface (first surface) in the phosphor layer 10 in contact with the substrate 3 in the layer thickness direction It is irradiated to the area of a fixed area on the side incident surface (second surface). The excitation light 6 that has entered the phosphor layer 10 from the incident surface travels while diffusing in the phosphor layer 10, and when absorbed by the phosphor particles 5, part of the energy becomes fluorescence light 7 and becomes fluorescence It is released from body particles 5 and other energy is released as heat.

The substrate 3 is formed of a material having high reflectance and thermal conductivity, such as metal (aluminum or the like) or sapphire or spinel coated with a reflection increasing coating for a fluorescent wavelength. The substrate 3 has the function of reflecting the excitation light 6 that has passed through the phosphor layer 10 and reached the substrate 3 and the fluorescent light 7 emitted from the phosphor particles 5 to the incident surface side. In addition, the substrate 3 is cooled on its back surface side (opposite to the phosphor layer 10) to promote heat dissipation from the phosphor layer 10.

The half portion (first portion) on the substrate contact surface side when the phosphor layer 10 is bisected in the layer thickness direction is referred to as the substrate side portion 10b, and the half portion (second portion) on the incident surface side Is referred to as the incident surface side portion 10a. At this time, as the phosphor layer 10 is enlarged and shown in the frame in FIG. 1, the volume density of the phosphor particles 5 in the substrate side portion 10b is higher than the volume density of the incident surface side portion 10a. Is formed. The volume density (vol%: hereinafter referred to as phosphor volume density) of the phosphor particles 5 referred to here is the ratio of the volume occupied by the phosphor particles 5 in the unit volume of the phosphor layer 10 (binder 4 and phosphor particles 5) It is. For example, FIG. 1 shows an example in which the phosphor volume density of the substrate side portion 10b is 58% while the phosphor volume density of the light incident surface side portion 10a is 38%. Thus, by controlling (setting) the volume density of the phosphor in the phosphor layer 10, the temperature gradient in the phosphor layer 10 is relaxed, that is, the temperature distribution is made to be uniform, cracking due to stress, etc. Can be suppressed.

FIG. 2 shows, as a comparative example, a wavelength conversion element 20 'whose phosphor volume density in the phosphor layer 10' is uniform in the layer thickness direction. Further, the heat distribution generated in the respective phosphor layers 10 and 10 'of FIGS. 1 and 2 is schematically shown on the lower side of FIGS. 3 and 4, respectively. In these figures, the dark part indicates high heat generation (high temperature) and the thin part indicates low heat generation (low temperature). Most of the heat generated in the phosphor layer is generated by the phosphor particles absorbing the excitation light and releasing part of it as heat rather than fluorescence. For this reason, the magnitude of heat generation per unit volume depends on the intensity of the incident excitation light and the phosphor volume density. Furthermore, the intensity distribution of the intensity of excitation light in the layer thickness direction (the depth direction from the incident surface) also depends on the phosphor volume density.

The upper side of each of FIG. 3 and FIG. 4 shows a state where the excitation light 6 incident on the phosphor layers 10 and 10 'travels in the phosphor layers 10 and 10'. The arrows in the figure indicate the traveling excitation light, and the thickness of the arrows indicates the intensity. As the excitation light travels in each phosphor layer, it travels while being diffused by diffusion factors such as phosphor particles and pores inside it, and a part is absorbed by the phosphor particles and converted into fluorescence light . That is, the excitation light travels while being attenuated in the depth direction under the two effects of the influence of internal diffusion and the absorption by the phosphor particles.

In the phosphor layer 10 ′ of the comparative example shown in FIG. 2 in which the volume density of the phosphor is uniform in the depth direction, strong heat generation occurs in the vicinity of the incident surface according to the high intensity of the excitation light. Then, as the excitation light travels in the depth direction, its intensity is attenuated. For this reason, as shown in FIG. 4, a heat distribution is generated in the phosphor layer 10 'that heat generation on the incident surface side is much larger than that on the substrate 3 side. As a result, as the relationship between the depth and the temperature in the phosphor layer 10 'is shown in FIG. 5, the temperature gradient in the depth direction in the phosphor layer 10' becomes large.

On the other hand, in the phosphor layer 10 of this example, the intensity of the excitation light 6 incident as shown in FIG. 3 is the same as that of the phosphor layer 10 'of the comparative example, but the fluorescence of the incident surface side portion 10a Since the body volume density is lower than that of the substrate side portion 10b, the amount of heat generation at the incident surface side portion 10a is suppressed. Furthermore, the excitation light reaches the substrate side portion having a high volume density of phosphors while being attenuated gradually in the phosphor layer 10 compared to FIG. 4 and is absorbed by many phosphor particles there. As a result, as also shown in FIG. 5, the temperature difference (temperature gradient in the depth direction) between the light incident surface side portion and the substrate side portion of the phosphor layer 10 is higher than that of the phosphor layer 10 'of the comparative example. It becomes smaller and the temperature distribution in the phosphor layer 10 becomes closer to uniformity than the phosphor layer 10 'of the comparative example.

Furthermore, a metal substrate is used as the substrate 3, and the cooling effect of the phosphor layer 10 can be further enhanced by cooling the back surface side of the substrate 3. At this time, since a higher cooling effect is obtained in the phosphor layer 10 closer to the substrate 3, the phosphor layer 10 of this example, in which the volume density of the phosphor particles and the intensity of the excitation light are both higher, is the comparative example. Higher heat dissipation effects can be expected compared to.

By configuring the wavelength conversion element 20 as described above, the occurrence of the temperature gradient in the phosphor layer 10 can be suppressed, and a high heat dissipation effect can be obtained. In particular, when the density of the excitation light irradiated to the phosphor layer 10 is very high, it is effective to use the wavelength conversion element 20 of this embodiment. Specifically, when the maximum intensity of the excitation light on the incident surface of the phosphor layer 10 is 10 W / mm ² or more, the effect obtained by the wavelength conversion element 20 of the present embodiment is large. More desirably, when the maximum intensity of the excitation light is 15 W / mm ² or more (more preferably 25 W / mm ² or more), the effect obtained is larger.

The phosphor volume density changes depending on the process of coating the phosphor layer 10 on the substrate 3 and the treatment such as baking, but can be determined from the weight ratio or mixing ratio of the phosphor particles to be used and the binder. As another practical evaluation method, obtain a surface SEM in a plane parallel to the incident surface or a cross-sectional SEM in the depth direction, and roughly obtain it from the area ratio of the region of phosphor particles to the binder or other regions. You can also. As a standard of the evaluation area in the case of using this evaluation method, it suffices to be sufficiently wider than the average particle diameter σ of the phosphor particles. In addition, "particle diameter" is a diameter when it converts into a sphere by the same volume. The “average particle size” is an average value of the particle sizes of all particles, but the average value of the particle sizes of all particles may be determined statistically from the particle sizes of some particles. The evaluation area that is sufficiently wide relative to the average particle size σ of the phosphor particles is, for example, an area whose side is about 2 to 100 times that of σ or an area whose area is 50 σ ² or more. Furthermore, it is desirable to evaluate using the average value in several evaluation area | regions.

In FIG. 1, for the sake of simplicity, the phosphor layer 10 is described as equally divided into the incident surface side portion 10a and the substrate side portion 10b, but in the phosphor layer 10, the phosphor volume density is gradually increased in the depth direction It is more desirable to change. For example, in the example shown in FIG. 6A, the volume density of the phosphor gradually changes in the depth direction to 35%, 45% and 65% over the incident surface side portion 10a, the intermediate portion 10c and the substrate side portion 10b (increase )doing. However, since the density distribution of the phosphor particles 5 fluctuates strictly depending on the particle size and the particle size distribution of the phosphor particles, the dispersion of the density in the range of the average particle size σ of the phosphor particles is neglected It is also good. In other words, as shown in FIG. 1, when the phosphor layer 10 is divided into two in the depth direction, the phosphor volume density of the substrate side portion 10b may be higher than that of the light incident surface side portion 10a.

More specifically, the phosphor volume density of the substrate side portion 10b is preferably 10% or more higher than the phosphor volume density of the light incident surface side portion 10a, and more preferably 15% or more. When the phosphor volume density of the substrate side portion 10b exceeds twice the volume density of the phosphor of the light incident surface side portion 10a, the density difference lowers the stability as a phosphor layer, resulting in cracking or breakage from the substrate 3. It is not desirable because peeling may occur.

In addition, if the volume density of the phosphor is less than 15%, it is necessary to increase the thickness of the entire phosphor layer in order to obtain sufficient brightness as the phosphor layer. When the thickness is increased, the size of the light source image formed by the light from the phosphor layer 10 (with respect to the optical system of the projector described later) is increased, which is not preferable because it becomes disadvantageous on the light capturing efficiency of the optical system. . On the other hand, when the volume density of the phosphor exceeds 70%, the ratio of the phosphor particles to the binder becomes too high, and the stability as the phosphor layer (film) decreases to cause cracking and peeling, which is not desirable. .

From the above, when the phosphor volume density (second volume density) of the incident surface side portion 10a is ρ0 and the phosphor volume density (first volume density) of the substrate side portion 10b is ρ1,
1.1 ≦ ρ1 / ρ0 ≦ 3.5
It is desirable to satisfy the following conditions. Also, with or without this condition,
25% ≦ ρ1 ≦ 70%
15% ≦ ρ0 ≦ 50%
It is desirable to satisfy the following conditions. The above conditional expression is
1.3 (more preferably 1.5) ≦≦ 1/1/0 ≦ 3.0 (more preferably 2.0)
45% ≦ ρ1 ≦ 70%
15% ≦ ρ0 ≦ 40%
It is better to satisfy one or more of them.

As the phosphor particles, a phosphor based on YAG (yttrium aluminum garnet) doped with Ce can be used. Other than that, any phosphor material such as LuAG type or sialon phosphor that absorbs ultraviolet to blue wavelength and emits light in green to red region in visible region can be appropriately selected and used.

Various methods can be used as a method of manufacturing the wavelength conversion element 20 (phosphor layer 10) in the present embodiment. For example, there is a method of dispersing phosphor particles in an inorganic binder made of silica, alumina, or a titania-based sol-gel material, and coating and drying. Besides, there is also a method of dispersing phosphor particles in glass or ceramics by mixing and sintering (sintering) glass ceramics and phosphor particles. At this time, if a high firing temperature is used, the characteristics of the phosphor particles may be degraded. Therefore, it is desirable to use a material such as low melting point glass as a binder.

In order to obtain phosphor layers 10 having different phosphor volume densities in the depth direction, for example, the following manufacturing method can be used. As a first method, two or more materials in which phosphor particles are dispersed in a binder before curing with different phosphor volume densities are prepared in advance, and those materials are viewed from the substrate 3 (or a base surface not shown) side. There is a method of applying and laminating in the order of high phosphor volume density. That is, a first material having phosphor particles dispersed at a first volume density in a binder, and a second material having phosphor particles dispersed at a second volume density higher than the first volume density in a binder Prepare the ingredients. Then, the first material and the second material may be stacked so that the second material is located on the substrate side. As shown in FIG. 6A, when there is an intermediate portion 10c having a third volume density intermediate between the first and second volume densities, the phosphor particles are dispersed in the binder at the third volume density. The third to third materials may be prepared, and the first to third materials may be stacked.

Thereby, it is possible to easily manufacture the phosphor layer 10 having the substrate side portion 10 b having the phosphor volume density higher than that of the incident surface side portion 10 a. Under the present circumstances, as shown in FIG.6 (b), you may mix the thing from which a particle diameter mutually differs as fluorescent substance particle 5 disperse | distributed to the material with high fluorescent substance volume density. Further, as shown in FIG. 6C, the other particles 8 different from the phosphor particles 5 are mixed into each material, and the density ratio of the phosphor particles 5 to the other particles 8 is made different depending on those materials. May be

As a second method, the phosphor layer 10 may be manufactured by a method of providing a difference in the volume density of the phosphor in the depth direction by precipitating the phosphor particles in a binder or glass before curing. In general, a mixture of materials having different specific gravities causes density deviation in the direction of gravity. For this reason, the phosphor layer of this example can also be disposed by setting the side with the higher volume density of the phosphor as the substrate side after controlling the coating conditions and the baking and cooling conditions to cause the density of the phosphor particles 5 to be uneven. 10 can be manufactured. However, when the density of the excitation light becomes very high, if a binder of an organic material is used, it may be thermally deteriorated and the stability and the life of the wavelength conversion element 20 may be reduced. Therefore, it is desirable that the phosphor layer 10 be made of only an inorganic material. Specifically, it is desirable that the binder be formed of oxide or nitride of silica or metal, or a mixture thereof.

The average particle diameter σ of the phosphor particles 5 is preferably in the range of about 1 to 10 μm. It is known that, when the average particle diameter σ of the phosphor particles is reduced, the light emission efficiency generally decreases due to the influence of the surface state of the phosphor layer. In the case of using phosphor particles having an average particle diameter σ of 1 μm or less, it is desirable to use after performing an improvement treatment such as surface modification for efficiency reduction. When the average particle diameter σ exceeds 10 μm, it is not desirable because the film thickness controllability and the variation in the in-plane density in the minute region may be concerned.

The layer thickness of the phosphor layer 10 is preferably in the range of 0.02 mm or more and 0.5 mm or less. If it is less than 0.02 mm, it is difficult to efficiently convert high density excitation light into fluorescent light. Further, if it exceeds 0.5 mm, there is a concern that the light capturing efficiency by the optical system of the projector may be reduced, and the phosphor layer 10 may be easily cracked. Further, the phosphor layer 10 desirably has a layer thickness of 5 times or more of the average particle diameter σ in terms of providing a volume density gradient in the layer thickness direction (depth direction).

Furthermore, as shown in FIG. 6C, inorganic particles may be mixed in the binder 4 as other particles 8 different from the phosphor particles 5. As a result, in the phosphor layer 10 having different phosphor volume densities, stress unevenness due to the difference in linear expansion between the phosphor particles 5 and the binder 4 or glass can be alleviated, the thermal conductivity can be improved, or the diffusion intensity of excitation light can be reduced. An effect such as control can be expected. As the inorganic particles used for such purpose, it is desirable to use those having an extremely low absorption at the wavelength of excitation light and a refractive index at the wavelength of excitation light different from that of the binder or glass material. When the difference in refractive index is too small, the interface reflectance of the inorganic particles is reduced, and the diffusion effect of the excitation light is reduced. Specifically, it is desirable to select inorganic particles having a refractive index difference of at least 0.05 (more preferably 0.10 or more) at the wavelength of excitation light or fluorescence.

When using inorganic particles for the purpose of relieving linear expansion, it is desirable that the material of the inorganic particles have a smaller linear expansion coefficient than, for example, the material of the phosphor particles or the binder. Furthermore, if a material having a negative linear expansion coefficient is used, it is possible to further suppress the bias of the stress generated in the phosphor layer. Thus, appropriate materials may be selected according to various purposes.

As mentioned above, although the wavelength conversion element 20 of a present Example was demonstrated, you may use the wavelength conversion element which has another structure. For example, although the reflection type wavelength conversion element 20 in which the phosphor layer 10 is formed on the metal substrate 3 is shown in FIG. 1, the substrate 3 may have translucency other than metal, in this case It can also be used as a transmission type wavelength conversion element. For example, it may be a dielectric material (sapphire or spinel) having high heat dissipation and close linear expansion coefficient.

In addition, as long as it can be supported by the phosphor layer 10 alone, the substrate 3 may be omitted. Even in this case, the effect of relaxing the temperature gradient can be obtained by making the phosphor volume density different in the phosphor layer 10 as in the present embodiment.

Further, a coating or a concavo-convex structure may be provided on the incident surface of the phosphor layer 10 or the substrate contact surface. By providing a reflection increasing film, a dichroic mirror or the like, improvement in light utilization efficiency, narrowing of the utilization wavelength, and the like can be expected. However, in a fine uneven structure, the shape (period, refractive index and occupancy rate) may change due to temperature change (linear expansion change) of the surface of the phosphor layer, and the effect of the uneven structure may be affected. By adopting the configuration described in the present embodiment, the stress of the phosphor layer can be relaxed, and in addition to the suppression of cracks and the like, the change in the uneven structure of the surface can be suppressed, and the light emission characteristics of the phosphor layer can be further enhanced. It can be stabilized.

As for the cooling means of the substrate 3, the wavelength conversion element 20 may be configured as a general rotating wheel body, micro driving with a piezo element may be performed, or a local cooling mechanism with a Peltier element may be used.

According to the present embodiment, by controlling the density of the phosphor particles in the phosphor layer 10, it is possible to suppress the generation of the temperature gradient due to the irradiation of the excitation light and prevent the generation of the stress due to the temperature gradient. Can be realized.

The thickness Th (mm) of the phosphor layer 10 in the present embodiment, the width in the radial direction of the phosphor layer formed in the annular shape is Wd (mm), the inner diameter (radius) of the annular shape, and the outer shape (radius) ) Is Ri (mm) and Ro (mm). Next, the area of the phosphor layer (the area of the surface having a ring shape, or the area when viewed from the light incident side) is Aph (square millimeter), and the substrate 3 on which this phosphor layer is formed. The area (area as viewed from the light incident side) is taken as Asu (square millimeter). Further, the energy of light incident on the phosphor layer 10 is Li (watts).

At this time, the thickness Th (mm) of the phosphor layer is preferably 30 μm to 200 μm (more preferably 35 μm to 120 μm, and further preferably 50 μm to 100 μm). In addition, the phosphor layer has an annular shape, and the width Wd of the annular shape and the thickness Th of the phosphor layer are
20 <Wd / Th <1000
(More preferably, 50 <Wd / Th <300, more preferably 120 or more)
It is desirable to satisfy By this configuration, heat can be efficiently dissipated from the phosphor layer toward the substrate.

Here, the width Wd of the annular shape of the phosphor layer is desirably 5 mm or more and 20 mm or less (more preferably 5 mm or more and 12 mm or less, and further preferably 8 mm or less).

When the outer diameter of the annular shape of the phosphor layer is Ro and the inner diameter is Ri,
1.05 <Ro / Ri <2.00
(More preferably, 1.10 <Ro / Ri <1.70, more preferably less than 1.40)
It is desirable to satisfy When the upper limit is satisfied, the substrate in the region inside the inner diameter can be secured at a certain level or more, and heat can be dissipated to the outside and the inside inside the substrate, which is advantageous from the viewpoint of heat dissipation. When the lower limit value is satisfied, it is possible to prevent the phosphor layer from being enlarged in the radial direction in order to dissipate heat. The inner diameter of the phosphor layer is desirably 40 mm or more and 100 mm or less (more preferably 40 mm or more and 80 mm or less, and further preferably 70 mm or less). The outer diameter of the phosphor layer is desirably 50 mm or more and 130 mm or less (more preferably 50 mm or more and 105 mm or less, and further preferably 85 mm or less).

Next, when the light intensity incident on the phosphor layer is Li (watts) and the area of the phosphor layer is Aph (square millimeter),
5 <Aph / Li <120 (mm ² / W)
(More preferably 5 <A / Li <60, still more preferably 6 <A / Li <40)
It is desirable to satisfy Here, it is desirable that the light intensity Li incident on the phosphor layer is 50 W or more and 500 W or less, more preferably 100 W or more and 500 W or less, and further preferably 250 W or more. The area Aph (square millimeter) of the phosphor layer is preferably 1000 or more and 10000 or less (more preferably 1500 or more and 6500 or less, and further preferably 3700 or less).

Also, the light intensity Li (watt) incident on the phosphor layer and the area Asu (square millimeter) of the substrate on which the phosphor layer is formed is 10 <Asu / Li <500 (mm ² / W)
(More preferably 20 <A / Li <260, still more preferably 30 <A / Li <100)
It is desirable to satisfy Further, the area Asu (square millimeter) of the substrate is desirably 5,000 or more and 100,000 or less (more preferably, 6,000 or more and 41,000 or less, and further preferably 10,000 or less).

In addition, the area Aph of the phosphor layer, the thickness Th of the phosphor layer, and the area Asus of the substrate are
3000 (mm) <Aph / Th <1,000,000 (mm)
(More preferably 8000 <Aph / Th <200000, more preferably 10000 <Aph / Th <58000)
1.50 <Asus / Aph <8.00
(More preferably 1.80 <Asus / Aph <7.00, more preferably 2.00 <Asus / Aph <4.00)
It is desirable to satisfy

The values of the above parameters are shown in detail in Table 1.

Next, a projector (image projection apparatus) 200 according to a second embodiment of the present invention will be described with reference to FIG. The projector 200 includes the light source device 100 described in the first embodiment. White light 102 (red light 102r, green light 102g, and blue light 102b indicated by a dotted line) emitted from the light source device 100 is incident on a projector optical system described below. First, red, green and

blue lights

102r and 102g and blue light 102b are incident on the polarization conversion element 103, where red, green and blue illumination lights (shown by dotted lines) 104r as linearly polarized light having a uniform polarization direction. , 104g, 104b.

These illumination lights 104r, 104g, and 104b are separated by the dichroic mirror 105 into red illumination light 104r, blue illumination light 104b, and green illumination light 104g. The green illumination light 104 g passes through the polarization separation element (hereinafter referred to as PBS) 108 and the phase compensation plate 112 and reaches the light modulation element 111 g. The red and

blue illumination lights

104 r and 104 b pass through the polarizing plate 106 and enter the color selective phase plate 107. The color selective phase plate 107 rotates the polarization direction of the blue illumination light 104 b by 90 ° while maintaining the polarization direction of the red illumination light 104 r as it is. The red illumination light 104r emitted from the color selective phase plate 107 passes through the PBS 109 and the phase compensation plate 112r to reach the light modulation element 111r. The blue illumination light 104b emitted from the color selective phase plate 107 is reflected by the PBS 109, passes through the phase compensation plate 112b, and reaches the light modulation element 111b. Each light modulation element is configured by a reflective liquid crystal panel or a digital micro mirror device. It is also possible to use a transmissive liquid crystal panel as the light modulation element.

The

light modulation elements

111g, 111r, and 111b perform image modulation on the incident green, red, and

blue illumination lights

104g, 104r, and 104b to convert them into green, red, and blue image lights 115g, 115b, and 115r. These image lights 115g, 115b and 115r are synthesized via the

PBSs

108 and 109 and the synthesis prism 118, and are projected by the projection lens 120 onto a projection surface such as a screen. Thereby, a color image as a projection image is displayed.

As described above, by using the light source device 100 described in the first embodiment, the projector 200 capable of stably displaying a bright projected image can be realized.

The embodiments described above are only representative examples, and various modifications and changes can be made to the embodiments when the present invention is implemented.

Claims

Having a phosphor portion in which phosphor particles are dispersed in a binder;
The phosphor portion has a first surface and a second surface opposite to each other in a thickness direction, and is a wavelength conversion element irradiated with excitation light from the second surface side,
The fluorescence at the first portion when the phosphor portion is bisected in the thickness direction into a first portion at the first surface side and a second portion at the second surface side A wavelength conversion element characterized in that a volume density of body particles is higher than the volume density in the second portion.
A substrate supporting the phosphor portion;
The wavelength conversion element according to claim 1, wherein the first surface is in contact with the substrate.
The wavelength conversion element according to claim 2, wherein the substrate is made of metal.
When the volume density in the first part is ρ1 and the volume density in the second part is ρ0,
1.1 ≦ ρ1 / ρ0 ≦ 2.0
The wavelength conversion element according to claim 1, wherein the following condition is satisfied.
When the volume density in the first part is ρ1 and the volume density in the second part is ρ0,
25% ≦ ρ1 ≦ 70%
15% ≦ ρ0 ≦ 50%
The wavelength conversion element according to claim 1, wherein the following condition is satisfied.
The wavelength conversion element according to claim 1, wherein a thickness of the phosphor portion is five or more times an average particle diameter of the phosphor particles.
Inorganic particles different from the phosphor particles are dispersed in the binder,
The wavelength conversion element according to claim 1, wherein the refractive index difference between the inorganic particles and the binder is 0.05 or more.
A light source emitting excitation light;
A light source device comprising the wavelength conversion element according to claim 1.
The light source device according to claim 8, wherein the intensity of the excitation light on the second surface of the phosphor portion is 10 W / mm 2 or more.
A light source device according to claim 8;
And an optical system for projecting an image by modulating light from the light source device with a light modulation element.
The binder has a phosphor portion in which phosphor particles are dispersed, and the phosphor portion has a first surface and a second surface opposite to each other in the thickness direction, and from the second surface side A method of manufacturing a wavelength conversion element to which excitation light is irradiated, comprising:
The first material in which the phosphor particles are dispersed with a first volume density in the binder, and the phosphor particles with a second volume density higher than the first volume density are dispersed in the binder Prepare the second material and
A method of manufacturing a wavelength conversion element, comprising laminating the first material and the second material such that the second material is positioned on the first surface side.